A study was conducted to determine the responses of soil enzymes （invertase, polyphenol oxidase, catalase, and dehydrogenase） to long-term CO2 enrichment at the Research Station of Changbai Mountain Forest Ecosystem...A study was conducted to determine the responses of soil enzymes （invertase, polyphenol oxidase, catalase, and dehydrogenase） to long-term CO2 enrichment at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences （42°24＇N, 128°28＇E; 738 m in elevation） in the northeast China during 1999-2006. Three treatments of the CO2 enrichment, designed as 500 μmol·mol-1 CO2 open-top chamber （OTC）, ambient control chamber and unchambered field （approx. 370 μmol·mol^-1CO2）, were conducted with Pinus koraiensis and Pinus sylvestriformis tree species. Soil sampling was made and analyzed separately in spring, summer and autumn in 2006 after the soil enzymes were exposed to elevated CO2 concentration （500 μmol·mol^-1） for eight growing seasons. Results showed that, at elevated CO2 concentration （500 μmol·mol^-1）, the activities of invertase （except for the summer samples of P. koraiensis） presented a remarkable decline in all growing seasons, while the activities of dehydrogenase had an increase but only part of the results was remarkable; the activities of polyphenol oxidase in P. sylvestriformis rhizosphere showed a remarkable decrease; the catalase activities increased in spring, while in turn were decline in other seasons. This study also revealed that the soil enzyme activities are significantly correlated with the tree species under the CO2 enhancement.展开更多
Soil enzymes play a vital role in biogeochemical cycling and ecosystem functions.In this study,we examined the response of six soil enzymes to changes in physicochemical properties resulting from changes in season and...Soil enzymes play a vital role in biogeochemical cycling and ecosystem functions.In this study,we examined the response of six soil enzymes to changes in physicochemical properties resulting from changes in season and vegetation and geological conditions.Catalase,urease,acid phosphatase,invertase,amylase,and cellulase not only promote carbon,nitrogen,and phosphorus cycling,but also participate in the decomposition of harmful substances.Thirty-six soil samples were collected from karst and non-karst areas in two different seasons and from three different types of vegetation in Yunnan province,southwest China.Both vegetation types and season had significant effects on soil physicochemical properties and enzyme activities.In the same plot,soil water content,electrical conductivity,organic carbon,total nitrogen,and total phosphorus increased in the rainy season,indicating enhanced microbial metabolic activity.With the exception of urease activity,the remaining five enzymes showed higher activity in the rainy season.Changes in activities between the two seasons were significant in all samples.In the same season,activity levels of soil enzymes were higher in karst areas than in non-karst areas,and higher in natural forest than in artificial forests.The transformative abilities of soil elements are higher in karst areas than in non-karst areas,and higher in natural forests than in artificial forests.Correlation analysis showed that the activities of the six enzymes correlated significantly;however,soil physical and chemical indices,such as organic matter,pH,and moisture,which are essential for enzyme activity,differed by season.Redundancy analysis also revealed that the main factors influencing enzyme activity differed between the two seasons.The results from this study provide a theoretical basis for further research on the restoration of natural ecological systems in karst landscapes.展开更多
Both climate and land-use changes,including the introduction and spread of allochthonous species,are forecast to affect forest ecosystems.Accordingly,forests will be affected in terms of species composition as well as...Both climate and land-use changes,including the introduction and spread of allochthonous species,are forecast to affect forest ecosystems.Accordingly,forests will be affected in terms of species composition as well as their soil chemical and biological characteristics.The possible changes in both tree cover and soil system might impact the amount of carbon that is stored in living plants and dead biomass and within the soil itself.Additionally,such alterations can have a strong impact on the detrital food web that is linked to litter decomposition.Although there are studies on the infuence of plant diversity on soil physical and chemical characteristics,the effects on soil biological activity and carbon storage processes remain largely unknown.The aim of this study was to investigate and compare chemical and biological variables in covariation with plant communities in an autochthonous beech forest(Fagus sylvatica L.)and a black pine plantation(Pinus nigra J.F.Arnold subsp.nigra).Our results confirmed that the two communities were considerably different,with the old-growth beech community having a lower number of plant species and the pine community was in development as a consequence of anthropogenic activities.These aspects of the two communities were also refected in the soil,with the beech soil having higher nitrogen levels and a more specialized microbial community compared to the pine soil,with most extracellular enzymes(such as peroxidase and chitinase)showing lower activity in the pine soil.展开更多
The continuing increase in human activities is causing global changes such as increased deposition of atmospheric nitrogen. There is considerable interest in understanding the effects of increasing atmospheric nitroge...The continuing increase in human activities is causing global changes such as increased deposition of atmospheric nitrogen. There is considerable interest in understanding the effects of increasing atmospheric nitrogen deposition on soil enzyme activities, specifically in terms of global nitrogen cycling and its potential future contribution to global climate change. This paper summarizes the ecological effects of atmospheric nitrogen deposition on soil enzyme activities, including size-effects, stage-effects, site-effects, and the effects of different levels and forms of atmospheric nitrogen deposition. We discuss needs for further research on the relationship between atmospheric nitrogen deposition and soil enzymes.展开更多
We used a litterbag method to investigate litter decomposition and related soil degradative enzyme activities across four seasons in a broad-leaved forest and a coniferous forest on Zijin Mountain in sub-tropical Chin...We used a litterbag method to investigate litter decomposition and related soil degradative enzyme activities across four seasons in a broad-leaved forest and a coniferous forest on Zijin Mountain in sub-tropical China. Across four seasons, we quantified litter mass losses, soil pH values, and related soil degradative enzyme activities. Litter decomposition rates differed significantly by season. Litter decomposi- tion rates of broadleaf forest leaves were higher than for coniferous for- ests needles across four seasons, and maximal differences in litter de- composition rates between the two litter types were found in spring.展开更多
In terrestrial ecosystems,deep soils(below 30 cm)are major organic carbon(C)pools.The labile carbon input could alter soil organic carbon(SOC)mineralization,resulting in priming effect(PE),which could be modified by n...In terrestrial ecosystems,deep soils(below 30 cm)are major organic carbon(C)pools.The labile carbon input could alter soil organic carbon(SOC)mineralization,resulting in priming effect(PE),which could be modified by nitrogen(N)availability,however,the underlying mechanism is unclear for deep soils,which complicates the prediction of deep soil C cycling in response to N deposition.A series of N applications with ^(13)C labeled glucose was set to investigate the effect of labile C and N on deep SOC mineralization.Microbial biomass,functional community,metabolic efficiency and enzyme activities were examined for their effects on SOC mineralization and PE.During incubation,glucose addition promoted SOC mineralization,resulting in positive PE.The magnitude of PE decreased significantly with increasing N.The N-regulated PE was not dependent on extracellular enzyme activities but was positively correlated with carbon use efficiency and negatively with metabolic quotient.Higher N levels resulted in higher microbial biomass and SOC-derived microbial biomass than lower N levels.These results suggest that the decline in the PE under high N availability was mainly controlled by higher microbial metabolic efficiency which allocated more C for growth.Structural equation modelling also revealed that microbial metabolic efficiency rather than enzyme activities was the main factor regulating the PE.The negative effect of additional N suggests that future N deposition could promote soil C sequestration.展开更多
Background:There is substantial evidence that Eucalyptus for nitrogen(N)absorption and increasing the growth benefit from the introduction of N-fixing species,but the underlying mechanisms for microbially mediated soi...Background:There is substantial evidence that Eucalyptus for nitrogen(N)absorption and increasing the growth benefit from the introduction of N-fixing species,but the underlying mechanisms for microbially mediated soil N cycling remains unclear.Methods:We investigated the changes of soil pH,soil water content(SWC),soil organic carbon(SOC),total N(TN),inorganic N(NH_(4)^(+)-N and NO_(3)^(-)-N),microbial biomass and three N-degrading enzyme activities as well as the biomass and N productivity of Eucalyptus between a pure Eucalyptus urophylla×grandis plantation(PP)and a mixed Dalbergia odorifera and Eucalyptus plantation(MP)in Guangxi Zhuang Autonomous Region,China.Results:Compared with the PP site,soil pH,SWC,SOC and TN in both seasons were significantly higher at the MP site,which in turn enhanced microbial biomass and the activities of soil N-degrading enzymes.The stimulated microbial activity at the MP site likely accelerate soil N mineralization,providing more available N(NH_(4)^(+)-N in both seasons and NO_(3)^(-)-N in the wet-hot season)for Eucalyptus absorption.Overall,the N productivity of Eucalyptus at the MP site was increased by 19.7% and 21.9%,promoting the biomass increases of 15.1% and 19.2% in the drycold season and wet-hot season,respectively.Conclusion:Our results reveal the importance of microbially mediated soil N cycling in the N absorption on Eucalyptus.Introduction of D.odorifera enhances Eucalyptus biomass and N productivity,improve soil N availability and increased soil C and N concentration,which hence can be considered to be an effective sustainable management option of Eucalyptus plantations.展开更多
Responses of soil microbial activities to elevated CO, in experiment sites of Pinus sylvestriformis and Pinus koratensts seecllmgs were studied in summer in 2003. The results indicated the number of bacteria decreased...Responses of soil microbial activities to elevated CO, in experiment sites of Pinus sylvestriformis and Pinus koratensts seecllmgs were studied in summer in 2003. The results indicated the number of bacteria decreased significantly （p 〈 0.05） under elevated CO, for Pinus syivestriformis and Pinups koraiensis. Amylase and invertase activities in soil increased for Pinus syivestriformis and decreased for Pinus koraiensis with CO2 enrichment compared with those at ambient （350 pmol·mol^-1）. The size of microbial biomass C also decreased significantly at 700 μmol- mol^-1 CO2. Bacterial community structure had some evident changes under elevated CO, by DGGE （Denaturing Gradient Gel Electrophoresis） analysis of bacterial 16S rDNA gene fragments amplified by PCR from DNA extracted directly from soil. The results suggested that responses of soil microorganisms to elevated CO2 would be related to plant species exposed to elevated CO2.展开更多
Changbai Mountain,central in the distribution of Pinus koraiensis,supports a virgin Korean pine forest with vertical gradient distribution.Soil extracellular enzyme activity(EEA) and enzyme stoichiometry(ES) are relia...Changbai Mountain,central in the distribution of Pinus koraiensis,supports a virgin Korean pine forest with vertical gradient distribution.Soil extracellular enzyme activity(EEA) and enzyme stoichiometry(ES) are reliable indicators of the energy and nutrients utilized by microbial communities and of soil nutrient changes.We measured four representative soil EEAs(sucrase,cellulase,urease,acid phosphatase) at two soil layers(A:0-5 cm and B:5-10 cm)beneath Korean pine forest at five elevations on Changbai Mountain during growing season.The vertical and seasonal variations of EEAs were analyzed by soil enzyme stoichiometry to quantify the role of soil microorganism in the nutrient cycling process.The activities of four soil extracellular enzymes and the ratios of enzyme activity to soil microbial biomass carbon(EA/SMBC) did not vary with elevation.The first partition point of multiple regression trees was in September,and the second branch was split by elevation.Seasonal change had more influence on soil enzyme activity(A layer:75.6%;B layer:71.3%) than did change in elevation(A layer:7.8%;B layer:7.5%).Over one entire growing season,both vector length and vector angle were unchanged by elevation,but varied significantly by month.Among the soil physicochemical factors,available phosphorus and pH were the main factors affecting the four soil EE As.The ratio of basal area of the coniferous tree to broad-leaved tree species(S_(con)/S_(br)),soil microbial biomass carbon(MBC) and nitrogen(MBN) influenced the four soil EE As.The results of vector analysis revealed that C and N sources were generally sufficient,but P was limiting(vector angle> 45°).The vector angle for September was significantly higher than for other months.This result verified that phosphorus was the limiting factor affecting soil microorganism function in nutrient metabolism and cycling.Soil enzyme stoichiometry proved to be an efficient index for quantifying soil microorganismmediated nutrient cycling in the Korean pine ecosystem.展开更多
We assessed the eff ects of arbuscular mycorrhizal fungi(AMF)Rhizophagus irregularis inoculation on salt stress tolerance in roots of the drought-tolerant plant Elaeagnus angustifolia.We studied a plant growth index,s...We assessed the eff ects of arbuscular mycorrhizal fungi(AMF)Rhizophagus irregularis inoculation on salt stress tolerance in roots of the drought-tolerant plant Elaeagnus angustifolia.We studied a plant growth index,spore density and hyphal length density of AMF,the Na+contents and ultrastructure of root cells,as well as rhizosphere soil enzyme activities of mycorrhizal and non-mycorrhizal E.angustifolia seedlings under diff erent salt stress.Under salt stress,growth of E.angustifolia with mycorrhizal inoculation was higher than that of non-inoculated treatments.The spore density and hyphal length density decreased signifi cantly under salt stress in rhizosphere soil of mycorrhizal E.angustifolia seedlings(p<0.05).The root cells of E.angustifolia seedlings inoculated with R.irregularis at 300 mmol L−1 salt had more organelles,greater integrity,and lower root Na+contents than those of non-inoculated seedlings.In addition,the results showed notably higher activities of catalase,phosphatase,urease and saccharase in rhizosphere soil of the mycorrhizal seedlings in response to salinity compared to those of the non-mycorrhizal seedlings.Therefore,AMF inoculation could enhance salt stress tolerance in roots of E.angustifolia.展开更多
基金This research was supported by National Basic Research Program of China (No.2002CB412502)Project of Key Pro-gram of the National Science Foundation of China (No.90411020)Natural Science Foundation of China (No.30400051)
文摘A study was conducted to determine the responses of soil enzymes （invertase, polyphenol oxidase, catalase, and dehydrogenase） to long-term CO2 enrichment at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences （42°24＇N, 128°28＇E; 738 m in elevation） in the northeast China during 1999-2006. Three treatments of the CO2 enrichment, designed as 500 μmol·mol-1 CO2 open-top chamber （OTC）, ambient control chamber and unchambered field （approx. 370 μmol·mol^-1CO2）, were conducted with Pinus koraiensis and Pinus sylvestriformis tree species. Soil sampling was made and analyzed separately in spring, summer and autumn in 2006 after the soil enzymes were exposed to elevated CO2 concentration （500 μmol·mol^-1） for eight growing seasons. Results showed that, at elevated CO2 concentration （500 μmol·mol^-1）, the activities of invertase （except for the summer samples of P. koraiensis） presented a remarkable decline in all growing seasons, while the activities of dehydrogenase had an increase but only part of the results was remarkable; the activities of polyphenol oxidase in P. sylvestriformis rhizosphere showed a remarkable decrease; the catalase activities increased in spring, while in turn were decline in other seasons. This study also revealed that the soil enzyme activities are significantly correlated with the tree species under the CO2 enhancement.
基金This work was supported by the National Key Research and Development Program of China(2016YFC0502500,2016YFC0502504)the National Natural Science Foundation of China(315005831008509)the Special fund for basic scientific research expenses of central public welfare scientific research institutes(CAFYBB2014ZD006,CAFYBB2016QB020).
文摘Soil enzymes play a vital role in biogeochemical cycling and ecosystem functions.In this study,we examined the response of six soil enzymes to changes in physicochemical properties resulting from changes in season and vegetation and geological conditions.Catalase,urease,acid phosphatase,invertase,amylase,and cellulase not only promote carbon,nitrogen,and phosphorus cycling,but also participate in the decomposition of harmful substances.Thirty-six soil samples were collected from karst and non-karst areas in two different seasons and from three different types of vegetation in Yunnan province,southwest China.Both vegetation types and season had significant effects on soil physicochemical properties and enzyme activities.In the same plot,soil water content,electrical conductivity,organic carbon,total nitrogen,and total phosphorus increased in the rainy season,indicating enhanced microbial metabolic activity.With the exception of urease activity,the remaining five enzymes showed higher activity in the rainy season.Changes in activities between the two seasons were significant in all samples.In the same season,activity levels of soil enzymes were higher in karst areas than in non-karst areas,and higher in natural forest than in artificial forests.The transformative abilities of soil elements are higher in karst areas than in non-karst areas,and higher in natural forests than in artificial forests.Correlation analysis showed that the activities of the six enzymes correlated significantly;however,soil physical and chemical indices,such as organic matter,pH,and moisture,which are essential for enzyme activity,differed by season.Redundancy analysis also revealed that the main factors influencing enzyme activity differed between the two seasons.The results from this study provide a theoretical basis for further research on the restoration of natural ecological systems in karst landscapes.
基金funding provided by Universitàdegli Studi della Campania Luigi Vanvitelli within the CRUI-CARE Agreement。
文摘Both climate and land-use changes,including the introduction and spread of allochthonous species,are forecast to affect forest ecosystems.Accordingly,forests will be affected in terms of species composition as well as their soil chemical and biological characteristics.The possible changes in both tree cover and soil system might impact the amount of carbon that is stored in living plants and dead biomass and within the soil itself.Additionally,such alterations can have a strong impact on the detrital food web that is linked to litter decomposition.Although there are studies on the infuence of plant diversity on soil physical and chemical characteristics,the effects on soil biological activity and carbon storage processes remain largely unknown.The aim of this study was to investigate and compare chemical and biological variables in covariation with plant communities in an autochthonous beech forest(Fagus sylvatica L.)and a black pine plantation(Pinus nigra J.F.Arnold subsp.nigra).Our results confirmed that the two communities were considerably different,with the old-growth beech community having a lower number of plant species and the pine community was in development as a consequence of anthropogenic activities.These aspects of the two communities were also refected in the soil,with the beech soil having higher nitrogen levels and a more specialized microbial community compared to the pine soil,with most extracellular enzymes(such as peroxidase and chitinase)showing lower activity in the pine soil.
基金supported by the National Natural Science Foundation of China (30970556, 31170386)Research Foundation for Advanced Talents, Jiangsu University (12JDG086)
文摘The continuing increase in human activities is causing global changes such as increased deposition of atmospheric nitrogen. There is considerable interest in understanding the effects of increasing atmospheric nitrogen deposition on soil enzyme activities, specifically in terms of global nitrogen cycling and its potential future contribution to global climate change. This paper summarizes the ecological effects of atmospheric nitrogen deposition on soil enzyme activities, including size-effects, stage-effects, site-effects, and the effects of different levels and forms of atmospheric nitrogen deposition. We discuss needs for further research on the relationship between atmospheric nitrogen deposition and soil enzymes.
基金supported by the National Natural Science Foundation of China(30870419,40971151)Strategic Priority Research Program Climate Change:Carbon Budget and Related Issues of the Chinese Academy of Sciences(XDA05050204)
文摘We used a litterbag method to investigate litter decomposition and related soil degradative enzyme activities across four seasons in a broad-leaved forest and a coniferous forest on Zijin Mountain in sub-tropical China. Across four seasons, we quantified litter mass losses, soil pH values, and related soil degradative enzyme activities. Litter decomposition rates differed significantly by season. Litter decomposi- tion rates of broadleaf forest leaves were higher than for coniferous for- ests needles across four seasons, and maximal differences in litter de- composition rates between the two litter types were found in spring.
基金supported by the Natural Science Foundation of China(Grant numbers 31870465,31600377,31700462).
文摘In terrestrial ecosystems,deep soils(below 30 cm)are major organic carbon(C)pools.The labile carbon input could alter soil organic carbon(SOC)mineralization,resulting in priming effect(PE),which could be modified by nitrogen(N)availability,however,the underlying mechanism is unclear for deep soils,which complicates the prediction of deep soil C cycling in response to N deposition.A series of N applications with ^(13)C labeled glucose was set to investigate the effect of labile C and N on deep SOC mineralization.Microbial biomass,functional community,metabolic efficiency and enzyme activities were examined for their effects on SOC mineralization and PE.During incubation,glucose addition promoted SOC mineralization,resulting in positive PE.The magnitude of PE decreased significantly with increasing N.The N-regulated PE was not dependent on extracellular enzyme activities but was positively correlated with carbon use efficiency and negatively with metabolic quotient.Higher N levels resulted in higher microbial biomass and SOC-derived microbial biomass than lower N levels.These results suggest that the decline in the PE under high N availability was mainly controlled by higher microbial metabolic efficiency which allocated more C for growth.Structural equation modelling also revealed that microbial metabolic efficiency rather than enzyme activities was the main factor regulating the PE.The negative effect of additional N suggests that future N deposition could promote soil C sequestration.
基金supported by the National Natural Science Foundation of China(No.31460196 and 31870461)the Innovation Project of Guangxi Graduate Education(No.YCBZ2018012),the“Hundred Talent Program”of South China Botanical Garden at the Chinese Academy of Sciences(No.Y761031001)+1 种基金the“Young Top-notch Talent”in Pearl River talent plan of Guangdong Provinceby the Science(No.2019QN01L763).
文摘Background:There is substantial evidence that Eucalyptus for nitrogen(N)absorption and increasing the growth benefit from the introduction of N-fixing species,but the underlying mechanisms for microbially mediated soil N cycling remains unclear.Methods:We investigated the changes of soil pH,soil water content(SWC),soil organic carbon(SOC),total N(TN),inorganic N(NH_(4)^(+)-N and NO_(3)^(-)-N),microbial biomass and three N-degrading enzyme activities as well as the biomass and N productivity of Eucalyptus between a pure Eucalyptus urophylla×grandis plantation(PP)and a mixed Dalbergia odorifera and Eucalyptus plantation(MP)in Guangxi Zhuang Autonomous Region,China.Results:Compared with the PP site,soil pH,SWC,SOC and TN in both seasons were significantly higher at the MP site,which in turn enhanced microbial biomass and the activities of soil N-degrading enzymes.The stimulated microbial activity at the MP site likely accelerate soil N mineralization,providing more available N(NH_(4)^(+)-N in both seasons and NO_(3)^(-)-N in the wet-hot season)for Eucalyptus absorption.Overall,the N productivity of Eucalyptus at the MP site was increased by 19.7% and 21.9%,promoting the biomass increases of 15.1% and 19.2% in the drycold season and wet-hot season,respectively.Conclusion:Our results reveal the importance of microbially mediated soil N cycling in the N absorption on Eucalyptus.Introduction of D.odorifera enhances Eucalyptus biomass and N productivity,improve soil N availability and increased soil C and N concentration,which hence can be considered to be an effective sustainable management option of Eucalyptus plantations.
基金The study was supported by Major State Basic Research Development Program of China (2002CB412502) and the Knowledge Inno-vation Project from Chinese Academy of Sciences (KZCX1-SW-01-03).
文摘Responses of soil microbial activities to elevated CO, in experiment sites of Pinus sylvestriformis and Pinus koratensts seecllmgs were studied in summer in 2003. The results indicated the number of bacteria decreased significantly （p 〈 0.05） under elevated CO, for Pinus syivestriformis and Pinups koraiensis. Amylase and invertase activities in soil increased for Pinus syivestriformis and decreased for Pinus koraiensis with CO2 enrichment compared with those at ambient （350 pmol·mol^-1）. The size of microbial biomass C also decreased significantly at 700 μmol- mol^-1 CO2. Bacterial community structure had some evident changes under elevated CO, by DGGE （Denaturing Gradient Gel Electrophoresis） analysis of bacterial 16S rDNA gene fragments amplified by PCR from DNA extracted directly from soil. The results suggested that responses of soil microorganisms to elevated CO2 would be related to plant species exposed to elevated CO2.
基金supported by the National Natural Science Foundation of China (No.31670496)。
文摘Changbai Mountain,central in the distribution of Pinus koraiensis,supports a virgin Korean pine forest with vertical gradient distribution.Soil extracellular enzyme activity(EEA) and enzyme stoichiometry(ES) are reliable indicators of the energy and nutrients utilized by microbial communities and of soil nutrient changes.We measured four representative soil EEAs(sucrase,cellulase,urease,acid phosphatase) at two soil layers(A:0-5 cm and B:5-10 cm)beneath Korean pine forest at five elevations on Changbai Mountain during growing season.The vertical and seasonal variations of EEAs were analyzed by soil enzyme stoichiometry to quantify the role of soil microorganism in the nutrient cycling process.The activities of four soil extracellular enzymes and the ratios of enzyme activity to soil microbial biomass carbon(EA/SMBC) did not vary with elevation.The first partition point of multiple regression trees was in September,and the second branch was split by elevation.Seasonal change had more influence on soil enzyme activity(A layer:75.6%;B layer:71.3%) than did change in elevation(A layer:7.8%;B layer:7.5%).Over one entire growing season,both vector length and vector angle were unchanged by elevation,but varied significantly by month.Among the soil physicochemical factors,available phosphorus and pH were the main factors affecting the four soil EE As.The ratio of basal area of the coniferous tree to broad-leaved tree species(S_(con)/S_(br)),soil microbial biomass carbon(MBC) and nitrogen(MBN) influenced the four soil EE As.The results of vector analysis revealed that C and N sources were generally sufficient,but P was limiting(vector angle> 45°).The vector angle for September was significantly higher than for other months.This result verified that phosphorus was the limiting factor affecting soil microorganism function in nutrient metabolism and cycling.Soil enzyme stoichiometry proved to be an efficient index for quantifying soil microorganismmediated nutrient cycling in the Korean pine ecosystem.
基金This work was supported by Key Laboratory of Microbiology,College of Heilongjiang Province.We would also like to thank Elizabeth Tokarz at the Yale University for her assistance with English language and grammatical editing of the manuscript.
文摘We assessed the eff ects of arbuscular mycorrhizal fungi(AMF)Rhizophagus irregularis inoculation on salt stress tolerance in roots of the drought-tolerant plant Elaeagnus angustifolia.We studied a plant growth index,spore density and hyphal length density of AMF,the Na+contents and ultrastructure of root cells,as well as rhizosphere soil enzyme activities of mycorrhizal and non-mycorrhizal E.angustifolia seedlings under diff erent salt stress.Under salt stress,growth of E.angustifolia with mycorrhizal inoculation was higher than that of non-inoculated treatments.The spore density and hyphal length density decreased signifi cantly under salt stress in rhizosphere soil of mycorrhizal E.angustifolia seedlings(p<0.05).The root cells of E.angustifolia seedlings inoculated with R.irregularis at 300 mmol L−1 salt had more organelles,greater integrity,and lower root Na+contents than those of non-inoculated seedlings.In addition,the results showed notably higher activities of catalase,phosphatase,urease and saccharase in rhizosphere soil of the mycorrhizal seedlings in response to salinity compared to those of the non-mycorrhizal seedlings.Therefore,AMF inoculation could enhance salt stress tolerance in roots of E.angustifolia.
